The present invention relates to an engine, and more particularly to an engine with a vibration suppression structure, comprising a cylinder block, cylinder head and a sheet metal gasket interposed between the cylinder block and the cylinder head.
In general, a power unit for a vehicle comprises an engine and a transmission. The transmission is coupled to an end surface of the engine where an output shaft protrudes therefrom (for the purpose of this specification, the side of the end surface is referred to as “rear side” and the opposite side is referred to as “front side” when the power unit is mounted on the vehicle).
Particularly, a housing that stores a clutch or a torque converter for the transmission is coupled to the rear end surface of the cylinder block, by use of a plurality of bolts that fasten a flange portion formed at the periphery of the front end of the housing to the rear end surface of the cylinder block.
In order to increase the coupling rigidity between the engine and the transmission for more bending stiffness of the entire power unit, it is preferred that a cylinder block of an engine and a housing of a transmission be coupled together via a large area. For this purpose, as shown in FIG. 9, a flange portion B1 is formed at the rear end of a cylinder block B of an engine A so as to reach the top portion of the cylinder block B, or a coupling surface between the cylinder block B and a cylinder head C. The flange portion B1 is brought into contact with a flange portion E1 of a housing E of a transmission D, and fastened thereto by bolts F.
For reinforcing the top portion of the flange B1 of the cylinder block B, a plate-shaped rib B2 may be formed which forwardly extends from behind the top portion of the flange B1 along the top end surface of the cylinder block B. In this case, the rib B2 projects outwardly and laterally with respect to the engine A from the rear top surface of the cylinder block B.
In the meantime, the side surface of the cylinder block B is constituted by a relatively thin wall, which tends to cause so-called membrane oscillation. To suppress the oscillation and the resultant noise, a rib may be formed on a side wall of a cylinder block as disclosed in Japanese Patent Application Publication 2009-156061. As mentioned above, however, the plate-shaped rib B2 projecting outwardly from the top end surface of the cylinder block B may unfavorably cause vibration which leads to another problem.
In more detail, when in the cylinder head C, fuel injectors are arranged immediately above the rib B2, the fuel injectors G cause so called ticking vibration resulting from the open/close motion of valves thereof, which is in turn transmitted to the rib B2 of the cylinder block B, possibly causing a resonance of the rib B2. This vibration of the rib B2 or membrane oscillation of the side wall of the cylinder block B caused by transmitted vibration of the rib B2 may cause the abovementioned problem.
In view of the abovementioned problem, it is an object of the present invention to provide an engine having a structure for suppressing a vibration of a projection laterally projecting from the side of a top portion of a cylinder head of an engine (such as a reinforcing rib for a flange used to couple the cylinder block with a transmission) and a noise caused by the vibration, while minimizing an increase in engine weight by use of a sheet metal gasket as an exiting part interposed between projections of cylinder block and a cylinder head.